Person:
KARAALP, ATİLA

Profile Picture

Email Address

Birth Date

Research Projects

Organizational Units

OrgUnit Logo
Organizational Unit

Job Title

Last Name

KARAALP

First Name

ATİLA

Name

Filters

1998 - 19992
Reset filters

Settings

Subject: ANTAGONIST ×

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    PublicationMetadata only
    Distinct functional muscarinic receptors in guinea-pig gallbladder, ileum and atria
    (ACADEMIC PRESS LTD, 1999) AKICI, AHMET; Karaalp, A; Akici, A; Akbulut, H; Ulusoy, NB; Oktay, S
    Objective. The contractile responses of guinea-pig gallbladder smooth muscle cells have been suggested to be mediated by M-3 and M-4 muscarinic receptors by different research groups. Therefore, in the present study, several pharmacological properties of cholinergic functions in guinea-pig gallbladder, guinea-pig ileum (mediated via M-3 receptors), and guinea-pig and rat atria (mediated via Mt receptors) were compared, Methods: The isometric contractions of isolated guinea-pig ileum, guinea-pig gallbladder, guinea-pig and rat atrial strips in in vitro organ bath were recorded on a polygraph and the effects of carbachol, oxotremorine, McN-A-343, and clozapine have been investigated. Results: Three muscarinic receptor agonists, carbachol, oxotremorine and McN-A-343 showed different order of potencies in their negative inotropic effects and contractile actions in guinea-pig gallbladder suggesting that functional muscarinic receptors in the gallbladder are distinct from those in the atria, and similar to M-4-subtypes. Clozapine which was shown to have antagonistic affinity for muscarinic M-1, M-2, M-3 and M-5, but partial agonistic affinity for muscarinic M-4 receptors, contracted gallbladder concentration-dependently. On the other hand, clozapine antagonised carbachol-induced ileal and gallbladder contractions and negative inotropic effects indicating that it acts like a partial agonist in the gallbladder. Conclusion: It was concluded that the contractile muscarinic receptors of guinea-pig gallbladder are distinct from those of atria (M-2) and ileum (M-3), but seem to be of M-4 subtype. (C) 1999 Academic Press.
  • No Thumbnail Available
    PublicationMetadata only
    Evidence for the presence of muscarinic M-2 and M-4 receptors in guinea-pig gallbladder smooth muscle
    (WILEY, 1998) KARAALP, ATİLA; Oktay, S; Cabadak, H; Iskender, E; Goren, Z; Caliskan, E; Orun, O; Aslan, N; Karaalp, A; Tolun, A; Ulusoy, NB; Levey, AI; El-Fakahany, EE; Kan, B
    1 The affinities of 10 selective muscarinic receptor antagonists against [H-3]-quinuclidinyl benzilate (QNB) binding were determined to characterize the muscarinic receptors present in guinea-pig gallbladder smooth muscle. The highest correlation was obtained for the comparison between the pK(i) values for the gallbladder smooth muscle and M-2 sites. Pirenzepine revealed two binding sites with affinities indicating the presence of muscarinic M-2 receptors in abundance and a minor population of an additional site(s). 2 Carbachol produced gallbladder contractions, stimulated phosphoinositide (PI) hydrolysis and inhibited cAMP formation concentration-dependently with pD(2) values of 6.12 +/- 0.11, 5.18 +/- 0.33 and 7.19 +/- 0.15, respectively. 3 Pirenzepine, 4-DAMP, HHSiD, pF-HHSiD, AF-DX 116, methoctramine, AQ-RA 741, guanylpirenzepine and AF-DX 384 showed competitive antagonism against carbachol-induced gallbladder contractions. There was no correlation between the pA(2) values for the gallbladder and pK(i) values for the M-2 sites, whereas significant correlations were found for the M-1, M-3 and M-4 sites, the best correlation being between the pA(2) values for the gallbladder and M-4 subtypes. 4 Finally, the presence of both m(2) and m(4) receptor proteins were demonstrated by Western blot analysis. It is concluded that guinea-pig gallbladder smooth muscle has both muscarinic M-2 and M-4 receptors, which are coupled to adenylate cyclase inhibition and PI hydrolysis. 5 Although it seems likely that Mt receptors do not play a primary role in carbachol-induced guinea-pig gallbladder contraction, the characterization of the muscarinic subtypes which mediate these contractile responses needs further evidence.